Research on Great White Sharks at Gansbaai – an evening at Marine Dynamics

At a recent Marine Evening hosted by Marine Dynamics at The Great White House in Gansbaai, PhD students Simone Rizzuto and Georgia French gave an overview of their research involving Great White Sharks to an animated audience.

In a ground breaking study Simone Rizzuto , a Marine Biologist from Italy, is researching the presence of pollutants in the ocean and their impact on the great whites, particularly with regard to their reproductive health. His results to date are very sobering and a cause for alarm. The pollutants include HCBs from the agricultural industry, PCBs from industry, DDT used by South Africa to combat malaria and PAHs from the oil and chemical industries. South Africa is one of the few countries in the world where the use of DDT has not been banned. According to Wilfred Chivell of Marine Dynamics and Dyer Island Trust, 274 tons of DDT were used in KZN between 2005 and 2008.

The pollutants reach the sea via the country’s waterways. They are also wind-borne. 28% of the oil and petroleum products of the Middle East are carried along the South African coastline, posing additional threats to our marine environment. This chemical soup of persistent organic pollutants (POPs) is extremely dangerous, their ingredients remaining active for hundreds years.

The primary consumers of these contaminants in the ocean are plankton. As one moves higher up the food chain, the concentration of POPs increase dramatically as the toxins are stored in the liver and fat of the animals. With the assistance of Marnie Dynamics and Dyer Island Conservation Trust Simone has been using “totally non-harmful methods” to collect tissue samples of the great white sharks of Gansbaai. He has found “alarming levels of POPs” in the first fifteen specimens of muscle tissues.

Luring a Great White to take tissue samples for research. Photo supplied by Simone Rizzuto

“The good news is that the great whites do have a detox system to may help protect them from the POPs,” says Simone, “but I need more samples to understand just how the detox system works.” Using two different proteins within the tissue to assess the reproductive health of his samples, he found that proteins normally found in mature female sharks are now being found in both immature males and females. Recently a sand shark caught near Hermanus was found to have both male and female gonads. “This is extremely worrying. If nothing changes, we may have a complete inversion of the sexes, leading to the extinction of the species. This phenomenon is also being seen in humans. We have to be very careful about what we eat. It is better to be eating food lower in the food chain where the concentrations of toxins are less and worse to be eating farmed fish as they are fed on other fish, including their livers, the organ of contamination. Whole fish are ground up as animal feed and fed to the animals that we eat” warns Simone.

Examining tissue from a great white shark. Photo supplied by Simone Rizzuto

Simone needs to take at least 100 samples to complete his study. These samples are being shared amongst the Universities of Stellenbosch, Cape Town and Sussex.

Working with shark tissue. Photo supplied by by Simone Rizzuto

Simone has a BSc in Biological Sciences and a Master’s degree in the Monitoring and Conservation of Marine Environments. Since 2011 he has been working on white shark (Carcharodon carcharias) conservation as a member of the Italian Research group Centro Studi Squali. In 2014 the University of Stellenbosch offered him a PhD position. Simone expressed his immense gratitude to Marine Dynamics and Dyer Island Conservation Trust for the assistance they have given him in his research.

Georgia French, zoologist from the UK, has a BSc in Zoology and a Master’s Degree in Wildlife Management and Conservation. For the past six months she has been working on her PhD on the ecological implications of personality in White Sharks. Her research includes the study of the shape of the teeth of the sharks as well as their feeding preferences.

Before expanding on her research on the Great Whites, Georgia gave a lively account of her work to date. After working on seabirds on several islands around the UK she undertook her Masters project on Sooty Terns in the Seychelles. “The Sooty Terns are considered the world’s most aerial bird. For the first five years of their lives they do not touch land. When they do they nest in huge colonies. Unfortunately most of their habitat in the Seychelles has been destroyed by coconut plantations, guano mining and coastal development. Their numbers have also declined as a result of the harvesting of their eggs.” Georgia was involved in the creation of a false colony on Denis Island, a fairly isolated 45 hectare island – a project which lasted for four years. Using 50 plastic models of the sooty tern and broadcasting the noise of a sooty tern colony, ultimately more than 250 terns were attracted to the new colony where they built nests and laid eggs, attracted primarily by the sound.

Models of sooty terns used in the Seychelles. Photo supplied by Georgia French

Georgia subsequently monitored the critically endangered Paradise Flycatchers on Denis Island after 23 birds were successfully translocated to the island, creating a vitally important second flycatcher population. Thereafter she was offered the position of Project Coordinator with the Marine Conservation Society of the Seychelles where she carried out an analysis of Baie Ternay Marine Park, an area of great biodiversity. This included a survey of the impact of anchor damage on the coral reefs by diving boats and the impact of harassment of marine species by the large numbers of divers and snorkelers using the bay. As a result, environmentally friendly mooring buoys were placed in the bay.. She also worked on the design of protected areas for whale sharks, another very vulnerable species, and measures were put in place to control boat traffic and boat speeds as boat strike is a mjor threat to whale sharks.

Leaving the tropical waters of the Seychelles, Georgia returned to the UK where she completed a six month contract with the Amphibian and Reptile Conservation Trust, evaluating the conservation status of highly protected Great Crested Newt, Britain’s largest newt, before embarking on her dream of completing a PhD on the Great Whites.

“The study of shark personalities is very important for ecological research. We need different personalities, and the variations in behaviour and possibly genetics that go hand in hand with them, for ecological balance. One of the simplest personality categories applied to sharks are shy vs bold which can include being dominant vs submissive. Personalities are currently being categorised by how they interact with bait and seal decoys, in addition to how they interact with each other.. The Great White sharks have complex social interactions and are very intelligent,” says Georgia.

Image of great white shark captured with laser apparatus. Photo: Georgia French

“The shape of the shark’s teeth changes throughout their lifetime. Sharks up to 3.5m in length generally have pointy teeth for holding and feeding on fish. Sharks of over 3.5m have broader teeth, to tear through the blubber of seals and dolphins. However, the tooth shape of some sharks do not change over time.” Georgia is studying the links between the shape of the teeth of the sharks and their personalities and also their food preferences and habitat use.

Georgia also expressed her gratitude for the assistance given her by Wilfred Chivell and his team at Marine Dynamics and Dyer Island Trust.